Fire Engineering Seminar BS 9991:2011 Fire Safety in the Design, management and use of residential buildings Martin Davidson Jeremy Gardner Associates
Traditionally prescriptive Reliance on Escape routes stairs, common corridors Containment by passive means Smoke detection Smoke venting in common areas.
BS 5588 Part 1 Maisonettes Alternative means of escape required where a floor > 4.5m above ground Only really worked for three storey buildings Problematic with taller buildings Common balconies for alternative means of escape Security and privacy issues Dual aspect units Can t get an alternative means of escape as there is no corridor on every floor.
BS 5588 Part 1 Smoke venting of common corridors Guidance very limited More than 1 stair 1m 2 Openable Vent Single Stair 1.5m 2 AOV. How many corridors connect directly with external? Vertical smoke shafts 1.5m 2 Open or closed at bottom? Alternative BRE Guidance Contentious
Travel distances BS 5588 Part 1 9m within apartments with kitchen away from exit Internal protected entrance hall with 9m travel distances Distances then unlimited within accommodation 7.5m single direction of travel in common corridor 30m where there is more than one stair
BS 5588 Part 1 Protected entrance halls Makes apartment entrance very dark Inefficient use of space Self closing fire doors Hazard to young children Disconnected by many No maintenance Effective?
Fires by Location
Fire Deaths by Location
BS 9991:2011 Published 31 December 2011 Supersedes BS 5588 Part 1 with immediate effect As with BS 9999, situation in Ireland as yet unclear TGD B currently being revised Deals with all parts of Building Regulations from B1 to B5. Similar in layout to TGD B More flexible design possible.
BS 9991:2011 Scope includes Houses Apartments and duplexes Sheltered housing Residential blocks (e.g. Student housing) Excludes Hotels, hospitals, nursing homes, hostels, prisons or houses of multiple occupancy.
Dwellings No changes for single or two storey houses 3 Storey Houses Alternative means of escape from top storey; or Protected stair; or Sprinklers throughout with fire separation of the ground from the upper floors Taller houses Floors >7.5m above ground should have an alternative means of escape or A protected stairway serving all floors plus sprinklers.
Apartment Blocks Residential buildings > 30m in height should be sprinklered Mechanical smoke ventilation for common corridors introduced Sprinklers and/or mechanical smoke ventilation recognised as alternative solution for extended travel distances in common corridors.
Balcony or Deck Approach Balcony should achieve 30 minutes fire resistance and be imperforate Should be designed to encourage smoke flow out and up. If more than 2m wide then downstands requried If there are voids in the balcony and there is a single direction of travel, unless the escape route is more than 1.8m away from the elevation a smoke analysis required.
Balcony Escape with Voids Flat Flat Flat >1.8m Single direction
Balcony with Single Direction of Escape Face of building should provide at least 30 mins (excluding windows) FD30 Doors Window openings should not extend below 1.1m above balcony Balustrade should be imperforate Walls, balcony and balustrade surfaces should be Class 0
Common Corridor to Flats or Maisonettes Travel distances have not changed from BS 5588 Part 1 7.5m in a single direction and 30m where there is an alternative Smoke ventilation provisions have changed More flexibility on extended travel distances depending on measures provided.
Smoke Control Where travel distances comply, primary purpose of smoke control is to protect the stair basis of stay put evacuation strategy Where travel distances are extended, primary objective is to protect both the stair and the corridor Natural or mechanical smoke ventilation Mechanical can be extract or pressurisation
BS 5588 Part 1 Ventilated
BS 9991 Smoke Control Where escape from flats is only via a corridor 7.4(a) the travel distance between the exit doors from the dwellings and a smoke-free area should be limited, and the amount of smoke and other combustion products in the internal corridor or lobby kept to a minimum by providing either cross corridor fire doors and ventilation, or a mechanical smoke ventilation system
Small Buildings with Single Stair Smoke venting of lobby not required where travel distances < 4.5m Stair can continue down to basement car park provided basement is ventilated and there is a ventilated lobby. 1m 2 OV at each level in stair or a single remotely operated vent at the top.
Section 26 Smoke Vent Single Stair > 11m Requirements 1.5m 2 AOV on the external elevation directly adjacent to the stair as high as possible and a 1m 2 AOV at the top of the stair; or 1.5m 2 vertical shaft directly adjacent to the stair as high as possible and a 1m 2 AOV at the top of the stair (fire fighting cores limited to 30m) ; or Mechanical extraction directly adjacent to the stair as high as possible and a 1m 2 AOV at the top of the stair
Mechanical Smoke Ventilation Usually incorporates a fan and a vertical shaft Where travel distance comply inlet via vent at top of stair Extended travel distances require inlet air provisions at each level Should shown better or equivalent conditions to the natural system using CFD analysis
Internal Layout of Flats Previous guidance retained Travel distances < 9m with no escape towards cooking areas Protected entrance hall with 9m travel distance Open plan flats permitted Sprinklers Size of flat < 16m x 12m Open plan flat should be single storey.
Internal Layout of Flats Open plan flats Ceiling height minimum 2.25m Where flat > 10m x 8m kitchen should be enclosed Where flat < 10m x 8m, kitchen can be open but located away from exit Open plan not permitted in sheltered housing.
Maisonettes Maisonettes < 4.5m above ground are the same as dwellings Maisonettes > 4.5m above ground have four options An alternative exit from any habitable room not on the entrance level A protected stair serving all rooms on upper level and 1 alternative exit A protected stair and LD1 detection if no floor >7.5m above or below entrance level A protected stair and sprinklers.
Variations Concept consistent with BS 9999 Where sprinklers fitted in flats travel distances can be increased In one direction from 7.5m to 15m More than one direction from 30m to 60m Extended travel distances can be addressed using mechanical ventilation.
Fire Fighting Facilities Buildings not fitted with fire mains Houses should have access to all areas to within 45m from appliance along route suitable for hose Flats should have vehicle access for a fire appliance not more than 45m from all points within each dwelling If sprinklers and no floor greater than 4.5m then distance can be increased to 90m in houses and 75m in flats provided fire brigade attendance time is less than 10m
Fire Fighting Facilities Fire fighting shaft required in buildings with floor greater than 18m (TGD B 20m) Sufficient number of fire fighting shafts should provided to meet hose coverage distances (60m) and at least two fire fighting shafts in a building with an area of more than 900m 2.
Fire Resistance Periods Error Why else would you bother?
Sprinklers Can be to BS 9251 if using table 3 ADB advises that limitations on the use of BS 9251 for buildings greater than 20m can be ignored If using table 4 then BS EN 12845 sprinkler system Tanks, pumps etc Any reductions in cost due to reduced fire resistance maybe cancelled out due to higher sprinkler system requirements.
Other Considerations Self-closing devices not required on fire doors within dwellings, flats or maisonettes except for door to communal areas Single stair building >11m stair should not continue down to basement unless it is sprinklered.
Other Considerations Lobby should have a falling dry main and be ventilated where it s a basement car park lobby vent should be 1m 2 AOV Currently current practice in Ireland is to provide double lobby protection in basement with one lobby ventilated with 0.4m 2 permanently open vent
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